Rear seal for servomotor

ABSTRACT

A combined seal and bearing member for aligning a force transmitting member of a servomotor. A U-shaped retainer frictionally held in an opening of the housing of the servomotor has a first leg surrounded by a resilient member. A hinged lip attached to the resilient member surrounds a tubular projection of the force transmitting member and seals the opening in the housing. A resilient wedge adjacent the first leg has its apex near a second leg of the U-shaped retainer. The second leg holds the bearing member which surrounds the tubular projection in contact with the resilient wedge. The resilient wedge will permit the bearing member to move transversely inside the retainer to align the tubular projection with the rear bearing of a power piston of a master cylinder.

United States Patent Julow 51 Apr. 3, 1973 REAR SEAL FOR SERVOMOTORPrimary Examiner-Martin P. Schwadron [75] Inventor: Thomas M. Julow,South Bend, Ind. 4 Zupclc Attorney-Leo H. McCormick, Jr. et al. [73]Assignee: The Bendix Corporation, South Bend Ind. 57 ABSTRACT I Filed:June 30, 1971 A combined seal and bearing member for aligning a [21]APPLNO; 158,327 force transmitting member of a servornotor. A U- shapedretainer frictionally held in an opening of the housing ofthe'servomotor has a first leg surrounded g' g gg by a resilient member.A hinged lip attached to the [58] Field of Search ..92/l68; 308/35,36.1, 26 g l? summds a Pmlectm "3 orce transmitting member and seals theopening in [56] References Cited the housing. A resilient wedge adjacentthe first leg has its apex near a second leg of the U-shaped UNITEDSTATES PATENTS retainer. The second leg holds the bearing member hichsurrounds the tubular ro'ection in contact with 1 P J g g if 92,168 theresilient wedge. The resilient wedge will permit the 3,215,477 11/1965 Ah bearing member to move transversely inside the 3,625,327 12/1971Birdsey retainer to align-the tubular projection with the rear 3,289,54712/1966 Kytta ..92/ 168 bearing of a power piston of a master cylinder.

4 Claims, 5 Drawing Figures REAR SEAL FOR SERVOMOTOR BACKGROUND OF THEINVENTION Servomotors are generally employed in power braking systems toprovide a power assist to the manual input force of the operator toenergize a master cylinder. In servomotors that are operated by partialvacuum and atmospheric pressure, the housing of the servomotor must besealed to provide an effective power assist. Normally, this type ofservomotor has a movable wall which is suspended in vacuum. The movablewall is connected to a hub which has a tubular projection extendingthrough an opening in the housing of the servomotor. The hub haspassageways connected to both sides of the movable wall. A control valvecarried inside the tubular projection is responsive to the manual inputforce transmitted by a push rod connected to the actuation pedal. Thecontrol valve will interrupt the vacuum supplied to one side of the wallwhile permitting atmospheric pressure to the other side thereby creatinga pressure differential. This pressure differential across the wall willdevelop a force which will move the hub and cause the tubular projectionto slide on a bearing member adjacent a seal in the opening of thehousing. As the hub moves, a corresponding output force is transmittedthrough a push rod to a power piston of a master cylinder.

The most effective output force will occur when the bearing surfaceholds the tubular projection in axial alignment with the power piston ofthe master cylinder.

In some instances misalignment can occur between the tubular projectionand the power piston because the opening in the housing is eccentric.When the bearing member is inserted in an eccentric opening, there isthe possibility that the bearing member will be cracked or, at least,increased frictional drag will be present upon moving of the tubularprojection by the wall. If the bearing member has been cracked, after anumber of brake applications which cause the tubular projection to move,the surface of the tubular projection will become scored. The scoredportion will act as a rasp as the wall moves and deteriorate the seal toa point where vacuum will not stay in the servomotor. Without vacuum,the servomotor will be inoperative and the power piston of the mastercylinder will have to be manually activated to supply the power to thebraking system for stopping a vehicle.

SUMMARY OF THE INVENTION To prevent damage to the tubular projection ofthe hub means in a servomotor and ultimately the seal closing theopening in the housing of the servomotor, I have invented a combinedbearing and seal means which will seal the opening and provide aresiliently positionable surface for axially aligning the hub means withan output member.

A U-shaped annular retainer has its front leg encased in a flexiblematerial and a lip is attached to this flexible material. An annularwedge of resilient material is placed between the front leg and the rearleg of the U- shaped retainer. Bearing means of a smaller diameter thanthe retainer is held in contact with an annular wedge of resilientmaterial by the rear leg, and this device frictionally placed in theopening in the servomotor. If the shape of the opening and the annularretainer are not exactly alike, the resilient wedge will be compressedas the U-shaped retainer is frictionally placed in the opening. In beingcompressed the axial alignment between the input member and the outputmember will be established and maintained without damaging the tubularprojection of the hub means since the bearing means can moveindependently of the U- shaped annular retainer.

It is therefore the object of this invention to provide a seal meanswith a bearing surface which can be shifted axially.

It is another object of this invention to provide a seal means capableof being inserted in an eccentric opening without internal damage to abearing surface contained therein.

These and other objects will become apparent to those who read thisspecification and view the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic illustration ofa power braking system showing the axial alignment of an input means, ahub means of a servomotor, an output transmitting means and a powerpiston of a master cylinder;

FIG. 2 is an exploded view of the circumscribed portion 2 of FIG. 1showing the seal and bearing means for aligning the hub means with theinput means;

FIG. 3 is a sectional view of the circumscribed portion 3 of FIG. 1;

FIG. 4 is a sectional view of another embodiment of the seal and bearingmeans for aligning the hub means with the input means;

FIG. 5 is a sectional view taken along line 5-5 of FIG. 4 showing thehub means positioned in the bearing means to be in alignment with theinput means.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT The power brakingsystem 10 shown in FIG. 1 is operated by partial vacuum created at theintake manifold 12 of a vehicle. The partial vacuum is communicatedthrough check valve 13 to a servomotor 14 which has a front shell 16joined to a rear shell 18 to form a housing. The interior of the housingis divided into a front chamber 20 and a rear chamber 22 by wall means24. The wall means 24 has a diaphragm 30 with an outer periphery 26 heldby the twist lock connector 28 which joins the front shell 16 to therear shell 18. The inner periphery 32 of the diaphragm 30 is snappedinto a groove 34 of hub means 36. A tubular projection 38 connected tothe hub means 36 extends through an opening 40 in the rear shell 18.Bearing means 42 holds the tubular projection 38 in axial alignment withthe power piston 68 of the master cylinder 70. Valve means 48 located inthe bore 50 of the tubular projection 38 controls the communication ofthe partial vacuum through a first passageway 52 from the front chamber20 of the servomotor 14 to the bore 50 and out a second passageway 54 tothe rear chamber 22. A push rod 56 has a head 58 retained in an annularopening 60 in the hub means 36 and spherical head 64 which extendsthrough a seal 62 of a type shown in U.S. Pat. No. 3,178,191 andincorporated herein by reference into a conical section 66 of the powerpiston means 68 of the hydraulic master cylinder 70.

In operation, an operator pushes on pedal 72 causing arm 46 to pivotaround pin 74. As arm 46 pivots on pin 74, an input force will becommunicated through pin 76 to input rod 44. The force from input rod 44will cause the plunger means 78 of the control means 48 to move andpermit resilient member 80 to seat a flexible member 82 on face 84closing the communication of partial vacuum through passage 52 to thebore 50. Further movement of the plunger means 78 will permitcommunication of air under atmospheric pressure through opening 86 intobore 50 out the second passageway 54 to the rear chamber 22.

With partial vacuum in the front chamber and air under atmosphericpressure in the rear chamber 22 a pressure differential will occuracross the wall means 24. The pressure differential pressure will act onthe area of the diaphragm 30 creating a force which will cause thetubular projection 38 to slide in bearing means 42 as the force istransmitted through push rod 56 to the power piston means 68. Movementof the power piston means 68 will pressurize fluid in the mastercylinder to operate the front 90 and rear 92 wheel brakes of thevehicle.

When the axial alignment between the input rod 44, the tubularprojection 38, the output push rod 56 and the power piston means 68 ismaintained, the most effective and efficient utilization of the forceproduced by the pressure differential will be achieved. With bearingmeans 42 and 94 properly positioned, this alignment will be achieved.Bearing means 94, which surrounds power piston means 68, is rigidly heldin bore 96 of the master cylinder 70. The position of bearing means 42which surrounds the tubular projection 38, alone is movable to permitaxial alignment to be adjusted.

In more particular detail, as shown in FIG. 2, the bearing means 42consists of an annular retainer member 96 which has a cylindrical body102 connected to an annular front leg 98 and an annular rear leg 100.The front annular leg 98 is encased with a first resilient means 104having a front face 106 with a portion 108 as shown by the dash line, toextend beyond the periphery of the retainer member 96. Upon insertion ofthe bearing means 42 into the opening 110 of the rear shell 18, portion108 is compressed and bulges as shown by bump 105 along the front face106 to resiliently seal the opening 110. A resilient lip 112 is attachedto the inner periphery 114 of the front face 106 by a thin annularportion 1 16. The thin annular portion 1 l6 acts as a hinge permittingthe lip 112 to extend on a bevel 117 toward and surrounding the tubularprojection 38. A recess 1 18 extends from the point of connection of thethin annular portions 116 with the inner periphery to the rear face 120of the first resilient means 104 which allows the lip 112 lateralmovement and yet maintains a seal as the tubular projection 38 movesaxially.

A second annular resilient means 122 has a cylindrical surface 124 whichabuts the inner periphery 126 of the cylindrical body 102 of theretainer member 96 and extends from the annular rear leg 100 to the rearface 120 of the first resilient means 104 separated from an annularsloping surface 128 by an annular wedge 130 having its apex 132 adjacentthe rear leg [00.

A bearing member 134 has an outer periphery 136 of a smaller diameterthan the inner periphery 126 of the cylindrical body 102 and an innerperiphery 138 which surrounds the tubular projection 38. The annularrear leg holds the outer periphery 136 of the bearing member 134 incontact with the sloping surface 128.

As the bearing means 42 is inserted in the opening 110, the cylindricalbody 102 will conform to the shape of the opening 110. Any eccentricityin the opening will not affect the bearing member 134 since the secondannular resilient means 122 will flow into the space provided by theannular groove 123 between the cylindrical surface 124 and the outerperiphery 136, as shown in FIG. 3. Thus, the bearing member 134 can movetransversely in the retainer member 96 to maintain the hub means 36 inaxial alignment with the bearing means 94 of the power piston.

The embodiment shown in FIG. 4 is the same as that shown in FIG. 2 withthe exception of the second resilient means 122 of FIG. 3. In the FIG. 4embodiment, the second resilient means is designated by the numeral 156and consists of a plurality of resilient flutes or hemispherical member158 radially positioned on the inner periphery 126 of the cylindricalbody 102. Upon holding the bearing member 134 in contact with the flutes158 by the rear leg 100 and insertion in opening 1 10, any eccentricityin the opening will be absorbed in the cylindrical body 102 which willcause the resilient flutes 138 to be distorted as shown in FIG. 5. Thisdistortion in the flutes will permit the bearing member 134 to movetransversely while maintaining axial alignment of the hub means 36 withthe power piston.

Thus, I have provided a servomotor with bearing means which will preventfrictional drag between the bearing surface and the movable hub meanscaused by eccentricity between the bearing retainer and the opening inthe servomotor. I have thereby eliminated the potential cause of manyservomotor failures and provided a bearing means with the capacity to beshifted to maintain axial alignment of the means transmitting the powerproduced in the servomotor and the power piston of an energizablehydraulic cylinder.

I claim:

1. A servomotor having a front shell secured to a rear shell to form ahousing for retaining wall means, said wall means being responsive to apressure differential to cause hub means connected thereto to move andtransmit an operational force through an output member to a power pistonof a master cylinder attached to the front shell, said hub means havingan annular projection held in an opening in the rear shell by bearingmeans, said bearing means maintaining the hub means in axial alignmentwith the power piston to directly transmit the operational force withoutbinding, said bearing means comprising:

an annular retainer member having a first end and a second end, acylindrical surface, said cylindrical surface having a first inner andouter periphery substantially parallel to the axial alignment betweenthe hub means and the power piston, said first outer periphery beingfrictionally retained in the opening in the rear shell, said first innerperiphery having a first annular groove adjacent said second end of thecylindrical surface;

a first annular leg attached to the first end of said cylindricalsurface extending toward the annular projection of said hub means;

first annular resilient means having a first annular portion with asecond outer periphery of a larger diameter than the opening in the rearshell, said first annular portion being secured to said first annularleg, said second outer periphery sealing the opening in the rear shelladjacent the first outer periphery of the annular retainer member;

a second annular portion secured to the first annular leg and the firstinner periphery of the annular retainer member, said second annularportion having a second groove therein;

a third annular portion for connecting the first and second annularportions together to form a unitary seal surrounding said first annularleg;

a resilient lip hingedly attached to said first annular portion andextending away from the first annular leg on a bevel toward the annularprojection of said hub means, said resilient lip surrounding saidannular projection to seal the opening in the rear shell, said secondgroove providing a holding space for a portion of said resilient lipwhen the resilient lip surrounds the annular projection of the hubmeans;

second annular resilient means secured to said second annular portion ofthe first annular resilient means, said second annular resilient meanshaving a bearing surface which abuttingly extends along the first innerperiphery and covers said first annular groove on the annular retainermember;

bearing means having an inner surface surrounding the annular projectionof the hub means and an outer surface contacting said bearing surfacecausing the second resilient means to radially flow into said firstannular groove permitting said bearing means to move transversely withrespect to said annular retainer member to alleviate any eccentricity insaid annular retainer during retention in said opening in said rearshell to thereby maintain said hub means in axial alignment with saidpower piston; and

a second annular leg attached to said second end of said cylindricalsurface of the retainer member for holding said bearing means in contactwith said second annular portion of the first annular resilient means.

2. The servomotor, as recited in claim 1, wherein said second annularresilient means includes:

a plurality of resilient flutes secured to said second annular portionof the first annular resilient means for positioning said bearing meansin said retainer means.

3. The servomotor, as recited in claim 1, wherein said second annularresilient means includes:

a cylindrical surface attached to the inner periphery of the retainermember and extending from the second annular portion of the firstannular resilient means to the second annular leg;

an annular sloping surface extending from the second annular leg to thesecond annular portion, said sloping surface permitting said bearingmeans to be moved within said retainer means to align said hub meanswith said power piston; and a surface abutting said second annularportion to support the sloping surface.

4. The servomotor, as recited in claim 1, wherein said second annularresilient means includes:

an annular wedge having an apex adjacent the second annular leg, saidannular wedge providing a varying surface for contacting the bearingmeans to permit the bearing means shift inside the annular retainermember and to align the annular projection of the hub means with thepower piston of the master cylinder.

1. A servomotor having a front shell secured to a rear shell to form a housing for retaining wall means, said wall means being responsive to a pressure differential to cause hub means connected thereto to move and transmit an operational force through an output member to a power piston of a master cylinder attached to the front shell, said hub means having an annular projection held in an opening in the rear shell by bearing means, said bearing means maintaining the hub means in axial alignment with the power piston to directly transmit the operational force without binding, said bearing means comprising: an annular retainer member having a first end and a second end, a cylindrical surface, said cylindrical surface having a first inner and outer periphery substantially parallel to the axial alignment between the hub means and the power piston, said first outer periphery being frictionally retained in the opening in the rear shell, said first inner periphery having a first annular groove adjacent said second end of the cylindrical surface; a first annular leg attached to the first end of said cylindrical surface extending toward the annular projection of said hub means; first annular resilient means having a first annular portion with a second outer periphery of a larger diameter than the opening in the rear shell, said first annular portion being secured to said first annular leg, said second outer periphery sealing the opening in the rear shell adjacent the first outer periphery of the annular retainer member; a second annular portion secured to the first annular leg and the first inner periphery of the annular retainer member, said second annular portion having a second groove therein; a third annular portion for connecting the first and second annular portions together to form a unitary seal surrounding said first annular leg; a resilient lip hingedly attached to said first annular portion and extending away from the first annular leg on a bevel toward the annular projection of said hub means, said resilient lip surrounding said annular projection to seal the opening in the rear shell, said second groove providing a holding space for a portion of said resilient lip when the resilient lip surrounds the annular projection of the hub means; a second annular resilient means secured to said second annular portion of the first annular resilient means, said second annular resilient means having a bearing surface which abuttingly extends along the first inner periphery and covers said first annular groove on the annular retainer member; bearing means having an inner surface surrounding the annular projection of the hub means and an outer surface contacting said bearing surface causing the second resilient means to radially flow into said first annular groove permitting said bearing means to move transversely with respect to said annulAr retainer member to alleviate any eccentricity in said annular retainer during retention in said opening in said rear shell to thereby maintain said hub means in axial alignment with said power piston; and a second annular leg attached to said second end of said cylindrical surface of the retainer member for holding said bearing means in contact with said second annular portion of the first annular resilient means.
 2. The servomotor, as recited in claim 1, wherein said second annular resilient means includes: a plurality of resilient flutes secured to said second annular portion of the first annular resilient means for positioning said bearing means in said retainer means.
 3. The servomotor, as recited in claim 1, wherein said second annular resilient means includes: a cylindrical surface attached to the inner periphery of the retainer member and extending from the second annular portion of the first annular resilient means to the second annular leg; an annular sloping surface extending from the second annular leg to the second annular portion, said sloping surface permitting said bearing means to be moved within said retainer means to align said hub means with said power piston; and a surface abutting said second annular portion to support the sloping surface.
 4. The servomotor, as recited in claim 1, wherein said second annular resilient means includes: an annular wedge having an apex adjacent the second annular leg, said annular wedge providing a varying surface for contacting the bearing means to permit the bearing means shift inside the annular retainer member and to align the annular projection of the hub means with the power piston of the master cylinder. 